Stress a killer for tiny lizards

It's official: stress is a killer, particularly if you're a sand lizard that has lost its tail.

Australian and Swedish researchers have found that telomeres, typically associated with ageing in humans, are affected by stress from attack and lead to a shorted lifespan for the tiny Swedish reptile.

Telomeres are sequences of non-coding DNA that cap the ends of chromosomes and contribute to their stability and the genomic integrity of cells.

They have been likened to the tips at the end of the shoelace that stops the shoelace from fraying.

In humans, "fraying" or shortening of telomeres can be increased by "factors leading to genetic erosion," says lead author Professor Mats Olsson, of the University of Wollongong.

Such factors can include free radicals and other forms of stress.

Professor Olsson and colleagues have looked at how a vital aspect of predator avoidance - tail autotomy, or dropping a tail - is linked to telomere length in the sand lizard, lacerta agilis.

The sand lizard - a small, ground-dwelling lizard found in Sweden - can only regrow its tail once if the whole tail is dropped.

"Once the last original vertebra in the tail is lost, there is no way to drop the tail 'voluntarily' under predator attack," Professor Olsson said.

"This in itself is likely to be highly stressful and seriously compromise survivorship."

In larger males, which have a much more exposed lifestyle, telomeres were significantly more affected by tail loss.

"Thus, males in the fast lane would be predicted to become more stressed during the mating season, and that is exactly what we see," the researchers write.

According to the study, males that are engaged in more contests for partners have higher corticosterone levels, which is the hormone involved in stress responses.

"These are exactly the same males in which tail regrowth most strongly seems to compromise telomere length."

The study appears in the online version of the journal Biology Letters.